This application claims the benefit of German Patent Application DE 10142488.4, filed Aug. 30, 2001, herein incorporated by reference.
The present invention relates to an opening arrangement for an open-end spinning device, in particular to an opening arrangement having a rotating opening roller having opening elements stationarily arranged on the circumference for opening a delivered sliver into individual fibers and for combing the fibers at a comb-out point.
In connection with open-end spinning processes, such as during friction spinning, as well as in connection with the rotor spinning process, fibers delivered into the spinning process are separated into individual fibers by means of an opening roller. In order to prevent the compression of fibers, it is customarily desired that the fiber material be constantly accelerated during its entire travel from the feeding device of the opening roller to the yarn withdrawal device, so that the fibers are maintained in a stretched state and are not compressed. In the course of this, the withdrawal speed should not become too great. As a result of this, the circumferential speed of the opening roller is limited, since it must be lower than the yarn withdrawal speed. The permissible number of revolutions of such an opening roller is clearly lower than the number of revolutions of an opening roller that is employed during the customary open-end rotor spinning process. The high circumferential speeds of the opening roller in rotor spinning contribute to the prevention of an uneven opening of the delivered fibers and an increased separation of fiber bunches which are not, or only incompletely opened. While in rotor spinning the opening roller customarily runs at a speed of approximately 8000 rpm, the number of revolutions of the opening roller in friction or air spinning, for example, is only 1800 rpm because of the above mentioned conditions. At such low numbers of revolutions of the opening roller the occurring centrifugal forces are reduced to such an extent that the detaching of the fibers from the opening roller is only insufficiently aided by the centrifugal forces. The transfer of fibers from the opening roller to the respective collecting device, for example a suction roller with a perforated surface, is correspondingly inadequate. To lessen the effects of this disadvantage at least somewhat, opening rollers are employed whose combing, or opening elements consist, for example, of needles which are not inclined in the running direction of the opening roller.
Customarily, opening elements of opening rollers are inclined at an angle of 15 to 20 degrees in the running direction of the opening roller in order to further the draw-in of the fibers and their combing-out of the free end of the delivered fibers, the so-called fiber tuft. The edge of the opening element that is in front in the running direction is called tooth face in connection with sets of saw-teeth, whose inclination in the running direction is called a positive face angle. However, a positive face angle makes the removal of the fibers from the opening roller more difficult.
Although the opening and transfer of delivered fibers which, for example, consist of 100% cotton, is possible with needles which have no inclination, the quality of the combing-out process suffers considerably from the omission of the inclination.
However, such measures are insufficient for the satisfactory opening and transfer to the collecting member of delivered fibers consisting of a mixture of polyester and cotton. After a short time, often after only a few seconds, the fibers begin to wind around the opening roller and the opening process is hampered in a sustained manner or even stopped.
A needle roller, between whose needles bendable rods have been placed, for feeding a sliver to the combing element of an open-end spinning device is known from German Patent Publication DE-AS 24 18 516. The rods are intended to replace an elastic cover of a known device in which the needles are embedded up to their tips, and to prevent the formation of a winding on the needle roller. The rods extend between two supports arranged on the two front faces of the roller and permit the compression, or concentration, of the fiber at the places where it rests against the rods. The sliver is pressed against the feed table by the rods. In order to exert this pressure, it is necessary for the sliver to be so compact and thick that it deflects the rods out of their position of rest. Thus, the employment of the bendable rods is limited to the feed device of an opening arrangement.
Swiss Patent Publication CH-PS 620 949 discloses a feed roller for a combing cylinder, which has needles conducted in radial bores of the feed roller surface. The needles are moved between a withdrawal and a push-out position. Hence, it is intended to improve the opening of the fibers between the feed roller and the combing roller. An arrangement with movable needles is mechanically complex and open to malfunctions. Due to the movement of the needles inward in a radial direction, fibers are pulled along into the gap between the needle and the roller surface and collect there. In the course of the subsequent extension of the needles, the fibers can become stuck in the radial bore and can block the needle by means of a wedge effect. The use of saw-teeth in place of needles is not possible here. Such arrangements have not been accepted.
With opening rollers rotating at a number of revolutions which is multiple times greater than the number of revolutions of a draw-in roller, additional air flows are created in order to affect the fiber conveyance and the opening process.
German Patent Publication DE 196 08 828 A1 shows an opening roller which is provided with openings for generating radial airflow at the circumference. The opening roller is equipped with a set of teeth.
However, the generation of airflow entails additional compressed air consumption at each spinning position, which represents a considerable cost factor in connection with spinning arrangements with a plurality of spinning positions. A further disadvantage when employing airflow is caused in that the speed of the airflow that exits from such a perforated roller is greater than the speed of a fiber just separated from the rollers. Due to this, the airflow blows against the fiber end and the fiber is compressed in an undesirable manner.
German Patent Publication DE 198 50 518 A1, which defines the species, shows an opening roller which, together with a support roller, combs out the fiber tuft. Additional compressed air consumption can be avoided for this reason. Although the opening of slivers is improved, the problem of the winding of fibers, or of an unsatisfactory transfer of the fibers from the opening roller to the collecting member, is not solved.
It is accordingly an object of the present invention to improve the function of the opening roller.
According to the present invention, this object is addressed by means of an opening arrangement for an open-end spinning device having a rotating opening roller with opening elements stationarily arranged on its circumference for opening a delivered sliver into individual fibers and for combing the fibers at a comb-out point, the rotating opening roller having a mechanical stripping arrangement that rotates along with the rotating opening roller.
It is possible with the opening roller of the present invention to lift fibers that, depending on the type of the opening element used, have been taken along by individual needles or teeth, in the area of the collecting member and to remove them from the opening elements, or from the set of teeth. The transfer of fibers from the opening roller to the collecting member is considerably improved. The extent of this improvement even permits the employment of needles or teeth of the opening roller having a positive face angle in order to perform better combing, without the fiber transfer from the opening roller to the collecting member again being impermissibly hampered, for example in connection with fibers that are difficult to process, or with fiber mixtures.
When employing airflow to aid in the functioning, the air pressure, and therefore the consumption of air, which aid in releasing the fibers by compressed air, can be considerably lowered in comparison to known devices. For example, the vacuum required for applying suction to an opening roller can be reduced from 130 mbar to 50 mbar. Stretching of the fibers during transfer is improved.
The winding tendency of fibers on the opening roller can be reduced or even stopped altogether at the low number of revolutions mentioned above. Even delivered fibers whose material consists of a mixture of polyester and cotton can be easily processed by the opening roller of the present invention.
In a preferred embodiment of the present invention, the opening arrangement has movable ejectors that are arranged between the opening elements and extend over the opening roller transversely in relation to the rotating direction and are preferably pivotably fastened on the opening roller. Preferably, one ejector is associated with every row of opening elements extending substantially transversely in relation to the rotating direction of the opening roller. When reaching the location on the circumference intended for the fiber transfer, such ejectors make it possible to simply provide the removal of the fibers carried along in a manner such that they are evenly distributed in width and functionally dependable.
In another preferred embodiment, the ejector is embodied as a wire hoop. This ejector can be simply and cost-effectively produced as well as easily fastened in bores on either side of the opening roller having only a small mass needing to be moved.
In yet another preferred embodiment, a stationary ring-shaped guide device for the ejectors is embodied and arranged in such a way that by its action the position of the respective circulating ejector in relation to the opening roller is cyclically changed. One cycle corresponds to one revolution of the opening roller. It is possible in this way to assign the position of the ejector in relation to the opening roller to the respective position on the circumference. In this case, the guide device has been advantageously designed in such a manner that the ejectors are forced to project between the opening elements because of the curved guide, wherein the respective circulating ejector projects the deepest between the opening elements when passing the comb-out location, and is lifted off the farthest from the base body of the opening roller at the point where the fibers separate from the opening roller. Thus, the fibers are always located above the ejector, and the stripping-off process can be performed without difficulty.
If the number of revolutions of the opening roller is so high that centrifugal force alone lifts the ejectors, a device providing an appropriate radial force, which is oriented outwardly from the opening roller, can be omitted. If the number of revolutions of the opening roller has been reduced too greatly to dependably lift the ejectors off the opening roller, the opening roller can have springs that provide an outward-directed force and, together with the centrifugal force, dependably cause the lifting of the ejectors.
The centrifugal force, as well as the spring force, press the ejectors against the ring-shaped guide device and assure that the ejectors rest against the inner surface of the guide device and follow the predetermined inner contours. Thus, it is an advantage that neither special drive mechanisms nor separate expensive control devices for moving the ejectors need to be provided.
In accordance with the present invention, the opening arrangement takes up little space and requires only a small outlay of additional components in comparison with a normal customary opening roller yet can be cost-effectively produced.
Aside from its employment with spinning processes wherein, because of the requirement for continuously stretched fibers, the number of revolutions of the opening roller is limited, the opening arrangement in accordance with the present invention is also suitable for employment with open-end rotor spinning frames for opening fibers there, that have a strong tendency to winding, for preventing circulating fibers, or the formation of laps, and to make possible gentler, lower numbers of revolutions of the opening rollers possible in connection with man-made fibers.
Further details of the present invention can be gathered from a non-limiting exemplary embodiment presented in the following description with reference made to the drawings.